HAMR thermal sensor with fast response time
Embodiments disclosed herein generally relate to a method for monitoring optical power in a HAMR device. In one embodiment, the method includes enhancing a thermal sensor bandwidth through advanced electrical detection techniques. The advanced electrical detection techniques include obtaining calibration waveform data for a thermal sensor by calibrating the thermal sensor, obtaining real-time waveform data for the thermal sensor that may deviate from the calibration waveform data, updating the calibration waveform data to include the real-time waveform data, repeating obtaining real-time waveform data and updating the calibration waveform data during writing operations. By updating the calibration waveform data, the bandwidth of the thermal sensor is determined by a fixed sampling time interval, and the thermal sensor rise time to steady state would not be a limitation to its response time.
1. A method, comprising:
obtaining calibration waveform data for a resistance of a thermal sensor;
measuring real-time waveform data for the resistance of the thermal sensor by sampling the resistance of the thermal sensor at a predetermined time interval, wherein the predetermined time interval corresponds to a bandwidth greater than a bandwidth of the thermal sensor;
determining deviated real-time waveform data;
updating the calibration waveform data to include the deviated real-time waveform data; and
repeating the measuring real-time waveform data, determining deviated real-time waveform data and updating the calibration waveform data.
2. The method of claim 1 , wherein the deviated real-time waveform data is greater than a predetermined threshold value.
3. The method of claim 2 , wherein the predetermined threshold value is at most one percent deviation from a resistance in the calibration waveform data.
4. The method of claim 1 , wherein the predetermined time interval ranges from about 5 nano seconds to about 20 nano seconds.
5. The method of claim 1 , wherein the deviated real-time waveform data is caused by a power fluctuation in a laser diode.
6. A method, comprising:
heating a thermal sensor to a predetermined temperature greater than an operating temperature of the thermal sensor;
maintaining the temperature of the thermal sensor at the predetermined temperature while the thermal sensor is operating at a steady state;
measuring and tracking a resistance value of the thermal sensor; and
maintaining the resistance value of the thermal sensor at a substantially constant value.
7. The method of claim 6 , wherein the predetermined temperature ranges from about 30 degrees Celsius to about 40 degrees Celsius.
8. The method of claim 6 , wherein the heating of the thermal sensor is performed by resistive heating.
9. The method of claim 6 , further comprising measuring and tracking a resistance of a reference sensor.
10. The method of claim 6 , wherein the maintaining the resistance value of the thermal sensor at the substantially constant value comprises increasing or decreasing a current flowing through the thermal sensor.
11. The method of claim 10 , wherein the increasing or decreasing the current flowing through the thermal sensor is performed by a preamplifier.
12. A method, comprising:
heating a thermal sensor to a predetermined temperature greater than an operating temperature of the thermal sensor;
obtaining calibration waveform data for a resistance of the thermal sensor;
obtaining real-time waveform data for the resistance of the thermal sensor;
updating the calibration waveform data to include the real-time waveform data;
repeating the obtaining real-time waveform data and updating the calibration waveform data;
maintaining the temperature of the thermal sensor at the predetermined temperature while the thermal sensor is operating at a steady state;
measuring and tracking a resistance value of the thermal sensor; and
maintaining the resistance value of the thermal sensor at a substantially constant value.
13. The method of claim 12 , wherein a deviation of the real-time waveform data from the calibration waveform data is greater than a predetermined threshold value.
14. The method of claim 13 , wherein the predetermined threshold value is at most one percent deviation from a resistance shown in the calibration waveform data.
15. The method of claim 12 , wherein the real-time waveform data is obtained by sampling the resistance of the thermal sensor at a predetermined time interval.
16. The method of claim 15 , wherein the predetermined time interval ranges from about 5 nano seconds to about 20 nano seconds.
17. The method of claim 12 , wherein the predetermined temperature ranges from about 30 degrees Celsius to about 40 degrees Celsius.
18. The method of claim 12 , wherein the heating of the thermal sensor is performed by resistive heating.
19. The method of claim 12 , wherein the maintaining the resistance value of the thermal sensor at the substantially constant value comprises increasing or decreasing a current flowing through the thermal sensor.